The present invention relates to a canister located in an evaporated fuel processing device.
Conventionally, as a canister which is located in an evaporated fuel processing device for preventing evaporated fuel (vapor) in a fuel tank on an automobile from leaking into the atmosphere, there has been proposed a canister of such a type that copes with an ORVR (Onboard Refueling Vapor Recovery) regulation, in which a plate is arranged in a absorbent charging chamber of the canister, and a constriction passage is formed in the plate in order to trap and process vapor in the fuel tank, in particular during refueling, without the vapor leaking into the atmosphere. This canister is disclosed in, for example, JP-A-06-249088 and JP-A-08-189428.
In such an ORVR regulation type canister, a conventional structure of the canister in which the above-mentioned plate is vertically arranged is shown in FIGS. 4 to 6.
The canister 1 shown in FIGS. 4 to 6, is composed of a main chamber 3 in which absorbent 2 including active carbon is charged, and a subchamber 4 in which the absorbent 2 is charged, and further, the subchamber 4 is partitioned into a first subchamber 4a and a second subchamber 4b by a plate 5 having constriction passages. The main chamber 3 and the first subchamber 4a are communicated with each other through a diffusion chamber 6.
The main chamber 3 and the subchamber 4 are arranged in a horizontal direction, and the plate 5 is arranged in a vertical direction.
A vapor introduction port 7 for sucking vapor (gasoline vapor) generated in a fuel tank during refueling, and a purge port 8 communicated with an air intake part of an engine are provided to the main chamber 3 on the side remote from the diffusion chamber 6. Further, there are shown absorbent holding filters 9, 10, an absorbent holding plate 11, and an absorbent holding spring 12.
An absorbent holding filter 13, an absorbent holding plate 14 and an absorbent holding spring 15 are provided in the first subchamber 4a on the diffusion chamber 6 side.
An atmospheric port 16 opened to the atmosphere is provided to the second subchamber 4b on the side remote from the plate 5. Reference 17 in the figures denotes an absorbent holding filter 17.
Several filter support pins 18 are projected from opposite surfaces of the plate 5, as arranged in FIG. 6. Filters 19, 20 for the plate are arranged at tip end faces of the filter support pins 18 on both surfaces of the plate, and the absorbent 2 is held by these filters 19, 20 while communication passages 21, 22 are defined between adjacent filter support pins 18. A constriction passage 23 which is a circular through-hole as shown in FIGS. 5 and 6 is formed in the plate 5, being located in its center upper part.
With this arrangement, at a time other than refueling, during resting of an engine, when liquid fuel in the fuel tank is evaporated so that the internal pressure becomes higher than a predetermined value, vapor in the fuel tank is introduced through the vapor introduction port 7 into the main chamber 3 in the canister 1, and the fuel component thereof is trapped by the absorbent 2. Then, the vapor has been introduced into the first subchamber 4a from the diffusion chamber 6 and a fuel component which has not yet trapped in the main chamber 3 is absorbed by the absorbent 2 in the first subchamber 4a. Further, the vapor passes through the filter 19 and ascends flowing through the communication passages 21 between the filter support pins 18 and between the plate 5 and the filter 19, and thereafter, passes through the constriction passage 23. Further, the vapor passes through the communication passages 22 and the filter 20, and enters into the second subchamber 4b in which a fuel component is trapped by the absorbent 2 in the second subchamber 4b. The vapor which is purified, substantially similar to the air after the fuel component is trapped, passes through the filter 17, and is vented into the atmosphere from the atmospheric port 16.
In such a case that is other than refueling, since the constriction passage 23 is formed at a position in the upper part of the plate 5, the vapor comes up from the lower side to the upper side as indicated by the arrows shown in FIG. 6, and the stream of the vapor is restrained and further, the discharge of the vapor from the atmospheric port 16 is restrained by the constriction passage 23.
Further, during refueling, the vapor whose pressure becomes higher in the fuel tank than that obtained in the case other than refueling, is introduced into the main chamber 3 from the vapor introduction port 7 due to its high positive pressure. The thus introduced vapor flows through the canister 1 so that the fuel component is trapped in the absorbent 2 in the chambers, similarly to above, and accordingly, the vapor having substantially become a purified gas which is similar to the air is vented into the atmosphere from the atmospheric port 16.
By the way, the volume of the vapor flowing into the canister 1 during refueling, is extremely large in comparison with that obtained in the case of other than refueling when the engine is rested. Accordingly, the air flow resistance among the filter support pins 18 of the plate 5 becomes higher during refueling. Therefore, if the flow distance among the filter support pins 18 is long, and if the flow resistance of the constriction passage 23 is high, the function of preventing the vapor from being discharged into the atmosphere become higher in the case of other than refueling, but the refueling speed becomes lower than usual so that the time of refueling is longer. On the contrary, if the above-mentioned passage resistance becomes lower in order to shorten the time of refueling, vapor which contains a fuel components by a large quantity is discharged into the atmosphere in the case of other than refueling. Accordingly, it is difficult that enhancing the prevention of discharge of vapor is consistent with the shortening of the time of refueling.
As the conventional plate 5 shown in FIG. 6, in the one in which a single constriction passage 23 is formed in the center upper part thereof, vapor which has flown into the first subchamber 4a from the diffusion chamber 6 comes up from the lower side to the upper side as indicated by the arrows in FIG. 6, and in particular, the vapor which flows on the opposite sides as indicated by the arrows A1, A2 has a long flowing distance to the constriction passage 23, and accordingly, it is difficult to shorten the time of refueling.
Accordingly, an object of the present invention is, as comparative with the conventional canister with the plate shown in FIG. 6, to provide a canister which can maintain the discharge of vapor into the atmosphere in the case of other than refueling, similar to the conventional canister 5, and further, which can aim at shortening the time of refueling.
To the end, according to the present invention, there is provided a canister which introduces vapor generated in a fuel tank thereinto through a vapor introduction port and then causes the vapor to flow through a chamber charged therein with an absorbent so as to purify the vapor, substantially similar to the air before it is vented from an atmospheric port, and in which a plate is vertically arranged in the chamber charged therein with the absorbent, the plate being formed in its upper part with a constriction passage means and being formed on its opposite surfaces with filter support pins having tip end faces at which filters are arranged,
wherein the constriction passage means is composed of a plurality of constriction passages which are arranged in a horizontal direction only in the upper part of the plate.
According to the present invention, during refueling, the volume and the pressure of vapor introduced into the canister are higher than that in the case of other than refueling, and the influence of the flow resistance of the vapor flowing among the filter support pins is high. With this arrangement, since the constriction passage means is composed of a plurality of constriction flow passages which are arranged in a horizontal direction, the flowing distance from the lower part of the plate to the constriction passage means becomes shorter, in average, than that of the conventional canister in which a single conventional constriction passage is formed in the upper part of the plate, and accordingly, the flow resistance (pressure loss) among the filter support pins 18 becomes smaller. Thus, the time of refueling can be shortened in comparison with the conventional one having a single constriction passage.
Further, in the case of other than refueling when the engine is rested, the volume and the pressure of vapor introduced into the canister are smaller than those during refueling. Accordingly, the influence of the flow resistance among the filter support pins is less, and therefore, the function of preventing discharge of vapor can be maintained, similar to the conventional one having a single constriction passage.
Further, in the present invention, the inner diameter of each of the plurality of constriction passages may be set to be equal to or smaller than a distance between adjacent those of the filter support pins.
Further, in the present invention, the relationship between the inner diameter D of each of the plurality of constriction passages and the distance L between adjacent those of the filter support pins may be set in a manner that L/D is in a range from 1 to 3.
With this arrangement, the influence of the flow resistance by the filter support pins can be further reduced, and the time of fueling can be effectively shortened.
Moreover, in the present invention, the plurality of constriction passages are composed of those having a larger diameter and those having a smaller diameter.
With this arrangement, technical effects similar to those as mentioned above can be exhibited, and the freedom of design can be enhanced in the case of less space in the horizontal direction of the plate.
In the above arrangement in which the constriction passages are composed of those having a larger diameter and those having a smaller diameter, the inner diameter of those having a smaller diameter may be set to be equal to or smaller than the distance between adjacent those of the filter support pins.
In the arrangement in which the constriction passages are composed of those having a larger diameter and those having a smaller diameter, the relationship between the inner diameter D of those having a smaller diameter and the distance between adjacent those of the filter support pins is set in a manner that L/D is in a range from 1 to 3.
Even with these arrangements, technical effects and advantages similar to that as mentioned above can be exhibited.